Bell Helicopter has confirmed the first test aircraft in the 525 Relentless programme crashed in central Texas on 6 July, killing two company test pilots and setting back a year-long effort to certificate the first application of fly-by-wire technology in a commercial helicopter.

“We’re working with relevant authorities to determine the cause of the accident and will provide further details as they come available,” says Bell in a statement released on Twitter.

The US National Transportation Safety Board (NTSB) added in a separate Twitter message that the crash occurred in “Chambers Creek”, Texas, which appears to be a reference to a small river about 120km southeast of Fort Worth.

Pictures of the crash scene indicate the wreckage belongs to the first 525 test aircraft, which launched the flight test phase on 1 July 2015.

Expected to enter service in 2017, the twin-engined 525 is packed with advanced technology. In particular, it represents the first application of fly-by-wire flight controls in a commercial helicopter. Combined with the Arc Horizon flightdeck system, the 525 computers assist the pilot by automatically holding the aircraft in hovers and banks.

The crashed aircraft was one of three prototypes involved in the flight test campaign so far. Two more test aircraft are expected to join the fleet in the third quarter.

In 2012, a two-member Bell flight crew walked away from a crash of a 214ST test aircraft, which was evaluating main rotor components intended for new helicopter models.